Santa Maria Island Geography
Santa Maria is located in the southeast corner of the Azores archipelago, 100km south of São Miguel, and 600km from the island of Flores (the western most island in the archipelago). The island is 97.4km² with an ovular shape. Geologically, it is the oldest island in the archipelago, with formations that are 8.12 million years old. Due to its age, and a lack of historical evidence of volcanic activity, the geography of the island tends to be more mature and includes larger deposits of sediments then can be found on the other islands of the archipelago. Similarly, marine fossils have been discovered on the island (in Prainha and Lagoinhas) that date back 117-130 million years (the Pleistocene epoch), and others, in Ponta do Castelo, dating back 5 millions of years (to the end of Mioceno and beginning of the Paleocene). These deposits are evidence of an older island environment associated with both volcanic and sedimentary development. Generally, Santa Maria is known for the lack of volcanic activity during period of human intervention, although seismic events are common due to its proximity to the Glória Fault: an offshoot of the Azores-Gibraltar Transform Fault.
Volcanic in origin, the geological makeup of Santa Maria is characterized by substrata of basalt deformed by a series of fractures in a northwest-southeast orientation. This is interlaced with lodes and deposits of silicate material. In addition, there are several calcium encrusted fossil deposits associated with marine formations during a period of formation associated with underwater activity. The presence of these deposits, unique in the Azores, gave rise to the lime (calcium oxide) industry during the 19th Century.